1/5 Scale Nike Hercules

[sambatterman]

Hello, I'm starting this chronicle of my 1/5 scale Nike Hercules build. It started in December 2021 and I'm hoping to fly it at MDRA in summer of 2022. Before we get into this, my goal for this project was to build a rocket that looks like a Nike Hercules, but that doesn't mean it operates exactly like it. This rocket is not clustered and does not stage. It's a single stage, single motor, level 2, low and slow model. My reasoning for this is as follows: this is a complicated and expensive rocket to build, and I'd like to fly it numerous times. Air starts of Nike Hercules on record usually "nuke" the booster (which is the most difficult part of the build (in my opinion). Additionally, there's not a lot of room for recovery for the booster to begin with, so we start this build with a number of compromises.

It's always good to get a ton of reference material, so here are the photos I have found most valuable during the build:



I started with an open rocket high level diagram and specification diagram:
This rocket will be approximately 9'5" long and about 30" in wingspan (booster fins). It will be around 70 lbs. loaded with motor and recovery materials.



Some things that are not completely obvious when looking at this model:

It's not clustered, but it "looks" clustered - I'm simulating this with a large body tube on the booster (the right most part of the rocket for the uninitiated). At apogee, the rocket will separate - booster drops back and pulls a drogue from the coupler and bottom portion of the sustainer (the left part of the rocket). The sustainer pops the nose cone, and a drogue will take the sustainer away from the booster. So, both bodies are falling under drogue until 1,000 feet where a tether on both the sections will fire, allowing the main chutes to pull from a deployment bag. Flying with dual altimeters (Perfectflite) on both booster and sustainer.

The sustainer has an avionics bay in the middle of the body tube that will manage the ejection fore and aft. There is no ejection charge in the booster - only pyro for the tether. The booster also has two altimeters (primary and backup) in the transitional shroud.

Next post, the booster build out.

 

[sambatterman]

Okay, let's get into the build of the booster. Overall, the booster is about 38" tall and it's built around a 6" blue tube body tube. I fiber glassed the tube to give it more strength and to create a strong core that the rest of the shell can be secured to. You can see in the photo below the "scalloped" internal structure that will hold the "booster" shells that give the appearance of a clustered model. In this shot the tiers of support are epoxied in place with vertical supports.

I also decided to run 1/4" all thread rods vertically - here they are in place, but not tightened or epoxied down.

I know it's early in the build, but I should share that these internal supports will hold 5.5" blue tube body tubes that are cut and epoxied in place on each support. This madness will be clearer in a minute.



Here's what it looks like with the skins dry fitted. Notice the rail button hard point pylon (padauk wood) that must be managed to fasten to the main body tube for strength and supported through the skin. Notice the fiber-glassed tubes are cut to allow for the 9 1/2" 3/8" birch fins (which are attached to the body tube for strength).



Notice the center ring and top and bottom bulkhead supports around the fins. Not only are the fins epoxied into the main body tube but they are mitered into the centering ring.

Also, notice the bottom plate is not a circle (!) it is a round-rectangle. This makes alignment of the fins a bit difficult. The bottom board is a jig to keep the fins aligned from side to side.

My biggest concern is that under power the outside shell (what looks like a clustered motor system would strip off like a banana peel, so there's a lot of internal strength being built into this. Interestingly the booster and the sustainer are opposite engineering problems. The sustainer strength is on the outside of the tube, but the booster strength is internal.

 

[sambatterman]

The motor mount is 75mm and around 32" long with a thrust plate at the bottom and Aeropack retainer container in a Mile High aluminum thrust plate. Two 1/4" all thread rods run the vertical distance between the thrust plate the recovery hard point. Remember how I said earlier in the thread about very little room for booster recovery? Here's why I said that. The motor mount is both epoxied and JB Welded into the central body tube. The hard point (which is 6/8" thick has a central U-Bolt for the main chute and will have a tether deployment mechanism to release the chute from a deployment bag held in the coupler (which we haven't shown yet). This hard point is also screwed into the "pedestal" support (bottom of the transition shroud) for extra connection and security.



The thrust plate is a Mile High aluminum thrust plate (a piece of art) with an Aeropack retainer for 75mm motors. I decided to use carbon fiber on the bottom plate to add some strength. This perspective shows how unique the fin can really is in appearance.

 

[sambatterman]

Shell glue up is next. Each "fake motor tube" is epoxied and foamed internally. You have to remember that a real Nike Hercules has a fin can that wraps around the bottom cluster and a shroud transition at the top. This one will too. The seams between the tubes are sealed with a thin fiberglass strip. Notice also the small hard wood stand offs for the rail button and on each side of the fin can a place for the birch panels to attach to - a preview of this is shown below. The entire bottom portion of the simulated motor tubes are all encased in the fin can.

 

[Rob Campbell]

Nice!

 

[captbk]

I would love to build another one bigger than I did. I am curious about the transition from booster to upper. Will you have one 3d printed? I carved mine from a block of balsa. I went with a 29mm motor but wish I went with 38mm. Flys great.

 

[sambatterman]

I would love to build another one bigger than I did. I am curious about the transition from booster to upper. Will you have one 3d printed? I carved mine from a block of balsa. I went with a 29mm motor but wish I went with 38mm. Flys great.

Thanks for sharing! Similar idea. Not 3d printing the fin can - it's too big. So, it's 1/8 birch panels (as you saw in the thread) and 1/8" vinyl sheets that cover the "round over." The entire panel will be fiber-glassed from fin root to fin root. I'm working on this currently and will have photos soon.

 

[Fattbank64]

I would love to build another one bigger than I did. I am curious about the transition from booster to upper. Will you have one 3d printed? I carved mine from a block of balsa. I went with a 29mm motor but wish I went with 38mm. Flys great.

Why 38mm?

Inquiring minds want to know

 

[captbk]

Why 38mm?

Inquiring minds want to know

More motor options.

 

[Raptor 2]

Shell glue up is next. Each "fake motor tube" is epoxied and foamed internally. You have to remember that a real Nike Hercules has a fin can that wraps around the bottom cluster and a shroud transition at the top. This one will too. The seams between the tubes are sealed with a thin fiberglass strip. Notice also the small hard wood stand offs for the rail button and on each side of the fin can a place for the birch panels to attach to - a preview of this is shown below. The entire bottom portion of the simulated motor tubes are all encased in the fin can.

View attachment 504173 View attachment 504176

Nice work. Way way above my brain grade. LPR scale is about all I can handle.

 

[Ez2cDave]

Why 38mm?

Hmm . . . 38mm . . . An Aerotech I357T ( Blue Thunder ) would be nice, for a starter. It would definitely "get it moving".

 

[Tim51]

Very interesting project, and nicely thought out. I imagine it will look great flying on AT White Lightning or CTI C- Star motors.

 

[rharshberger]

Hello, I'm starting this chronicle of my 1/5 scale Nike Hercules build. It started in December 2021 and I'm hoping to fly it at MDRA in summer of 2022. Before we get into this, my goal for this project was to build a rocket that looks like a Nike Hercules, but that doesn't mean it operates exactly like it. This rocket is not clustered and does not stage. It's a single stage, single motor, level 2, low and slow model. My reasoning for this is as follows: this is a complicated and expensive rocket to build, and I'd like to fly it numerous times. Air starts of Nike Hercules on record usually "nuke" the booster (which is the most difficult part of the build (in my opinion). Additionally, there's not a lot of room for recovery for the booster to begin with, so we start this build with a number of compromises.

It's always good to get a ton of reference material, so here are the photos I have found most valuable during the build:
View attachment 504155 View attachment 504156 View attachment 504157
View attachment 504158 View attachment 504159 View attachment 504160

I started with an open rocket high level diagram and specification diagram:
This rocket will be approximately 9'5" long and about 30" in wingspan (booster fins). It will be around 70 lbs. loaded with motor and recovery materials.

View attachment 504154

Some things that are not completely obvious when looking at this model:

It's not clustered, but it "looks" clustered - I'm simulating this with a large body tube on the booster (the right most part of the rocket for the uninitiated). At apogee, the rocket will separate - booster drops back and pulls a drogue from the coupler and bottom portion of the sustainer (the left part of the rocket). The sustainer pops the nose cone, and a drogue will take the sustainer away from the booster. So, both bodies are falling under drogue until 1,000 feet where a tether on both the sections will fire, allowing the main chutes to pull from a deployment bag. Flying with dual altimeters (Perfectflite) on both booster and sustainer.

The sustainer has an avionics bay in the middle of the body tube that will manage the ejection fore and aft. There is no ejection charge in the booster - only pyro for the tether. The booster also has two altimeters (primary and backup) in the transitional shroud.

Next post, the booster build out.

Care to share the OR file, I have a smaller version I need to sim and modding yours would be way easier than creating one from scratch? Uh Please?

 

[Arsenal78]

You sure it’ll be 70lbs loaded and still be able to fly on a Level 2 motor? A very high thrust L might do it but that’s more of a Level 3 motor weight. I could be wrong though but all the M motor flights I’ve seen were 40+lbs.

 

[sambatterman]

Care to share the OR file, I have a smaller version I need to sim and modding yours would be way easier than creating one from scratch? Uh Please?

Sure - here you go...

 

[Ez2cDave]

You sure it’ll be 70lbs loaded and still be able to fly on a Level 2 motor? A very high thrust L might do it but that’s more of a Level 3 motor weight. I could be wrong though but all the M motor flights I’ve seen were 40+lbs.

I was going to say that amount of that All-Thread was "overkill" and only adds unnecessary mass, but I didn't. It's way overbuilt, in my opinion.

At 70 lbs., with a 3:1 minimum thrust to weight ratio, that requires 210 lb of thrust, for a sufficient duration to get it up to flight speed. At 5:1, that becomes 350 lb of thrust.

Motor choice will be critical . . .

Dave F.

 

[sambatterman]

You sure it’ll be 70lbs loaded and still be able to fly on a Level 2 motor? A very high thrust L might do it but that’s more of a Level 3 motor weight. I could be wrong though but all the M motor flights I’ve seen were 40+lbs.
[/QUOTE
I've flown a 7.5" Bullpup that was 55-60 pounds on level 2 motors with no issues. I'll let you know though; I'm getting close to finishing the booster (no paint) and it's coming in around 30 lbs. The sustainer has less going on structurally.

 

[dbpeirce]

I finished a 1/6 scale version this winter and hope to get it in the air this spring. Good luck with your build. Keep up the post.
Here is a photo of mine. 4 38mm cluster and a single 54mm in the sustainer. The electronics and recovery will be tricky but I believe I have it figured out.

 

[sambatterman]

I finished a 1/6 scale version this winter and hope to get it in the air this spring. Good luck with your build. Keep up the post.
Here is a photo of mine. 4 38mm cluster and a single 54mm in the sustainer. The electronics and recovery will be tricky but I believe I have it figured out.
View attachment 504409

What a beautiful rocket! Are those parts 3d Printed? I'm currently working on the shroud (transition between sustainer and booster). How are you handling recovery for the booster, since you are airstarting the sustainer? Where are you storing the chute?

 

[dbpeirce]

The booster will utilize the interstage coupler as its nose and use motor ejection to deploy two chutes. There will be a separation charge for the sustainer and electronics for that, the sustainer ignition and chute deployment are in a bay in the transition of the nose. There is plenty of room for the sustainer chute below that (but no way to do traditional dual deploy due to the sustainer fins running the full length) but it will have to come out with a drogue at apogee and use a chute release for final deployment of the main.

 

[dbpeirce]

There are some parts I printed, including the interstage coupler.
There are some pictures of the process on a build thread I did here on the forum.

1/6th (approximately 😁)Nike Hercules build

Starting on this build I’ve been thinking about for some time now. It is based on some blue tube booster airframe I got from a member here a couple years ago. Because I’m starting from this it is gonna end up being less than real scale I suppose, but close enough to attempt the build anyway...

www.rocketryforum.com

 

[sambatterman]

The booster will utilize the interstage coupler as its nose and use motor ejection to deploy two chutes. There will be a separation charge for the sustainer and electronics for that, the sustainer ignition and chute deployment are in a bay in the transition of the nose. There is plenty of room for the sustainer chute below that (but no way to do traditional dual deploy due to the sustainer fins running the full length) but it will have to come out with a drogue at apogee and use a chute release for final deployment of the main.

Sounds well thought out. I'm using drogues and tethers to cut to the main chute as well. Can't wait to see yours fly.

 

[sambatterman]

I was going to say that amount of that All-Thread was "overkill" and only adds unnecessary mass, but I didn't. It's way overbuilt, in my opinion.

At 70 lbs., with a 3:1 minimum thrust to weight ratio, that requires 210 lb of thrust, for a sufficient duration to get it up to flight speed. At 5:1, that becomes 350 lb of thrust.

Motor choice will be critical . . .

Dave F.

Hi Dave - thanks for the comment. I'm used OpenRocket to sim this on many motors - landing mostly on L1120W - which would take it to 2700 ft. I've also looked at M1297W and M178ONT - both of which sim to around 3200 ft. With the motor mount I installed I should have a number of choices. As for the all-thread, my big concern is the abrupt jerking of the rocket when the chute opens and I didn't want the internal supports to shear off. There are a lot of examples of overbuilt rockets that use more all thread and supports than I am. I'm doing my best to be durable and light and this is a tricky build.

 

[sambatterman]

Hi Dave - thanks for the comment. I'm used OpenRocket to sim this on many motors - landing mostly on L1120W - which would take it to 2700 ft. I've also looked at M1297W and M178ONT - both of which sim to around 3200 ft. With the motor mount I installed I should have a number of choices. As for the all-thread, my big concern is the abrupt jerking of the rocket when the chute opens and I didn't want the internal supports to shear off. There are a lot of examples of overbuilt rockets that use more all thread and supports than I am. I'm doing my best to be durable and light and this is a tricky build.

An L2200 from Aerotech looks like it gets it done. Thanks for stimulating my brainpan on this.

 

[Ez2cDave]

I'm using drogues and tethers to cut to the main chute as well.

As for the all-thread, my big concern is the abrupt jerking of the rocket when the chute opens and I didn't want the internal supports to shear off. There are a lot of examples of overbuilt rockets that use more all thread and supports than I am. I'm doing my best to be durable and light and this is a tricky build.

If you are using a Drogue, or Drogues, the descent velocity should be relatively low ( less than 50 - 75 ft/sec +/- ). So, there should be no huge "shock" when the parachute opens, especially if folding techniques are used to slow deployment. The Main Chute(s) will not "boom open", under those circumstances. Certainly, the opening forces would be substantially less than the forces incurred during powered flight.

Assuming a 70-lb Liftoff Wt. ( your number ) . . .

( 1 ) M1297W = 5.4 G's
( 2 ) M1780NT = 6.8 G's
( 3 ) L1120W = 5.1 G's

M1297W

************************************************************************************************
M1780NT

************************************************************************************************
L1120W

************************************************************************************************

Dave F.

 

[sambatterman]

The interstage transition is almost done.


notice the avionics bay in the interstage coupler for firing pyro for the tether to the booster chute.

 

[dbpeirce]

Cool!

 

[rharshberger]

The interstage transition is almost done.
View attachment 504973 View attachment 504974 View attachment 504975 View attachment 504976 View attachment 504977 View attachment 504978

notice the avionics bay in the interstage coupler for firing pyro for the tether to the booster chute.

Its easy to make a posterboard wrap transition to cover that, just use the upper diameter, and the measurement (circumference of the bottom of the 4 into 1) of the bottom around the entire edge of the transition, then lay it out just like you would an Estes LPR transition, its how I did mine. I used 110lb cardstock then hardened it with CA.

 

[sambatterman]

Its easy to make a posterboard wrap transition to cover that, just use the upper diameter, and the measurement (circumference of the bottom of the 4 into 1) of the bottom around the entire edge of the transition, then lay it out just like you would an Estes LPR transition, its how I did mine. I used 110lb cardstock then hardened it with CA.

View attachment 504980 View attachment 504981 View attachment 504982

Very cool, Rich! I'm using fiberglass after I sand down the filler. I like the look of your interstage coupler though.

 

[Adam3836]

Looks awesome

I finished a 1/6 scale version this winter and hope to get it in the air this spring. Good luck with your build. Keep up the post.
Here is a photo of mine. 4 38mm cluster and a single 54mm in the sustainer. The electronics and recovery will be tricky but I believe I have it figured out.
View attachment 504409